Radio scanners have become an important tool in a wide range of applications from police, fire and rescue operations to hobby and sports recreation.
Generally, a set of receiving frequencies, referred to as channels, can be entered into the scanner that will be periodically monitored for transmission signals according to some predefined automatic algorithm. When a signal of sufficient strength is found in a channel, the scanner "locks" onto that channel to permit the user to hear or record the content of the signal in the channel. That is, the scanner stays tuned to the active channel for some period of time and does not immediately move on to examine another channel of the specified set. Depending upon the available options, the scanner may remain tuned to the channel indefinitely, or it may dwell on the channel only for a fixed period of time and then resume scanning of the set of channels, even though the transmission in the channel has not terminated. If there is no transmission of sufficient amplitude in a channel when it is examined, the scanner simply moves on to examine other channels in the specified set for activity.
In many applications, it is important, or even vital, for the user to have immediate knowledge of the channel to which the scanner is currently tuned. For example, in police, fire and rescue work, different agencies utilize different frequencies, or channels, for their operations. Immediate knowledge of the channel over which a transmission is heard can be essential in emergency decision making because of the equivalency of the received channel number and the source of the information conveyed.
Another example is provided by sports car racing. Pit crews, drivers, mechanics, etc. all use radio transmissions to communicate. Given the number of cars at a race and the number of participants who must all communicate, it is possible that upwards of hundreds of frequencies may be in use. To ensure that race participants will be able to communicate without mutual interference, frequencies are assigned and published prior to the event. Monitoring of these frequencies by spectators using scanners has become a significant source of relevant information for spectators following the progress of a race. Here, as in emergency work, proper interpretation of the significance of a transmission depends critically upon knowledge of the channel over which a transmission is heard because of the association of the assigned channels with specific race participants.
As important as the channel number is, in both of these examples, there is generally a high degree of activity that leaves little, or no, free time to determine the channel over which a transmission is heard.
Scanners known in the prior art employ LCD (Liquid Crystal Display) or LED (Light Emitting Diode) visual character displays to indicate the frequency, or corresponding channel number, to which the scanner is currently tuned. These devices suffer from the serious disadvantage in periods of high activity that they require the user to focus his or her attention on the visual display in order to determine the channel number. Consequently, the user is distracted from other important activities. Since, in circumstances of high activity, transmissions may be received in rapid succession over many different channels in no predictable order, the user's attention potentially can be dominated by the task of ascertaining the channel, and hence source, of transmissions. On the other hand, failure to pay close attention to the channel number may result in misunderstanding and improper decision making with serious consequences.
Accordingly, it would be desirable if the scanner channel number could be conveyed by a voice or other audible identification, thereby freeing the user's attention for other tasks. Even more desirable would be audible annunciation of more immediately meaningful information correlated with the channel number. That is, rather than, or in addition to, simple identification of the channel number, it would be desirable if the scanner could provide other audible information such as the name of the emergency unit or the race car driver assigned to the channel.
Since the relationship between the channel number and the assignee to the channel, or other information, is likely to change over time, it would also be desirable that means be provided for the user to enter and change custom annunciations associated with each scanner channel. And, because the number of channels that must be set could be quite large, it would also be desirable that means be provided for uploading and downloading whole sets of channel frequencies and associated annunciations thereby freeing the user of the tedium, and possible error, associated with manual entry.